Communication device for establishing multiple links with multiple component carriers

ABSTRACT

A communication device comprises a computer readable recording medium, and a processor, for processing a program code to execute a process; wherein the process comprises: establishing a first link corresponding to a first component carrier of the plurality of component carriers, by performing a first radio resource control (RRC) procedure; establishing at least a link corresponding to at least a component carrier of the plurality of component carriers other than the first component carrier, by performing a second RRC procedure which is performed according to a first RRC message received in the first link; and performing a random access procedure for synchronization of the at least one link established by the second RRC procedure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/617,953, filed on Feb. 10, 2015, which is a continuation of U.S.application Ser. No. 12/541,982, filed on Aug. 17, 2009, which claimsthe benefit of U.S. Provisional Application No. 61/160,713, filed onMar. 17, 2009, the contents of which is included in its entirety hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method utilized in a wirelesscommunication and communication device thereof, and more particularly,to a method of establishing multiple links with multiple componentcarriers in a wireless communication system and related communicationdevice.

2. Description of the Prior Art

Long Term Evolution wireless communication system (LTE system), anadvanced high-speed wireless communication system established upon the3G mobile telecommunication system, supports only packet-switchedtransmission, and tends to implement both Medium Access Control (MAC)layer and Radio Link Control (RLC) layer in one single communicationsite, so that the system structure becomes simple.

Toward advanced high-speed wireless communication system, such astransmitting data in a higher peak data rate, LTE-Advanced isstandardized by the 3rd Generation Partnership Project (3GPP) as anenhancement of LTE system. LTE-Advanced targets faster switching betweenpower states, improves performance at the cell edge, and includessubjects, such as bandwidth extension, coordinated multipointtransmission/reception (COMP), uplink multiple input multiple output(MIMO) extension up to 4×4, downlink MIMO extension up to 4×4, relaying,and etc.

Based on a concept of bandwidth extension, carrier aggregation isintroduced to the LTE-Advanced for extension to wider bandwidth, wheretwo or more component carriers are aggregated, for supporting widertransmission bandwidths e.g. up to 100 MHz and for spectrum aggregation.According to carrier aggregation capability, multiple component carriersare aggregated into overall wider bandwidth, wherein a user equipment(UE) can establish multiple links corresponding to the multiplecomponent carriers for simultaneously receiving and/or transmitting oneach component carrier.

Each component carrier includes a hybrid automatic repeat request (HARQ)entity and a transport block. That is, each component carrier in theLTE-Advanced works independently.

As abovementioned, the UE can utilize multiple component carriers fortransmitting and/or receiving data in LTE-Advanced. However, the priorart does not clearly teach how the UE shall establish multiple linkswith multiple component carriers.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a method of establishingmultiple links with multiple component carriers in a wirelesscommunication system and related communication device.

A communication device capable of establishing multiple links withmultiple component carriers in a wireless communication systemsupporting carrier aggregation is provided. The communication device isconfigured with a plurality of component carriers of the wirelesscommunication system for realizing carrier aggregation. Thecommunication device comprises a computer readable recording medium forstoring a program code corresponding to a process; and a processorcoupled to the computer readable recording medium, for processing theprogram code to execute the process; wherein the process comprises:establishing a first link corresponding to a first component carrier ofthe plurality of component carriers, by performing a first radioresource control (RRC) procedure; establishing at least a linkcorresponding to at least a component carrier of the plurality ofcomponent carriers other than the first component carrier, by performinga second RRC procedure which is performed according to a first RRCmessage received in the first link; and performing a random accessprocedure for synchronization of the at least one link established bythe second RRC procedure.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication system withmultiple component carriers.

FIG. 2 is a schematic diagram of a communication device according to anembodiment of the present invention.

FIG. 3 is a flowchart of a process according to a first embodiment ofthe present invention.

FIG. 4 is a flowchart of a process according to a second embodiment ofthe present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which illustrates a schematic diagram ofconnections between a UE and cells C1-Cn. In FIG. 1, the cells C1-Cn andthe UE are communicated through links L1-Lm each corresponding to acomponent carrier configured in the UE, and each support a LTE radioaccess technology (RAT) or an E-UTRAN (Evolved Universal TerrestrialRadio Access Network) RAT. For example, the UE is communicated with thecell C1 through the link L1, communicated with the cell C2 through thelinks L2-L4, and so on. Normally, the UE performs a random accessprocedure for uplink synchronization and initial cell access.

Please refer to FIG. 2, which illustrates a schematic diagram of acommunication device 20 according to an embodiment of the presentinvention. The communication device 20 can be the UE shown in FIG. 1 andincludes a processor 200, a computer readable recording medium 210, acommunication interfacing unit 220 and a control unit 230. The computerreadable recording medium 210 is any data storage device that storesstorage data 212, including a program code 214, thereafter read andprocessed by the processor 200. Examples of the computer readablerecording medium 210 include a subscriber identity module (SIM),read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetictapes, hard disks, optical data storage devices, and carrier waves (suchas data transmission through the Internet). The control unit 230controls the communication interfacing unit 220 and related operationsand states of the communication device 20 according to processingresults of the processor 200. The communication interfacing unit 220 ispreferably a radio transceiver for wirelessly communicating with thenetwork (i.e. the cells C1-Cn).

The program code 214 includes a program code of a RRC layer which canestablish links L1-Lm corresponding to component carriers. The RRC layeris used for performing RRC connection establishment, re-establishment,reconfiguration, or other RRC procedures, and is responsible forgenerating or releasing radio bearers (RBs) including data RBs (DRBs)and signaling RBs (SRBs). Through use of the SRBs, the RRC layer and thecells C1-Cn can exchange RRC messages for radio resource settings.

Please refer to FIG. 3, which illustrates a flowchart of a process 30according to a first embodiment of the present invention. The process 30is utilized in the UE for establishing multiple links corresponding tomultiple component carriers. The process 30 can be compiled into theprogram code 214 and includes the following steps:

Step 300: Start.

Step 302: Establish a first link corresponding to a first componentcarrier by a first RRC procedure.

Step 304: Establish at least a link corresponding to at least acomponent carrier by a second RRC procedure according to a first RRCmessage received in the first link.

Step 306: End.

According to the process 30, the UE performs RRC procedures to establisha plurality of links corresponding to a plurality of component carriers.The first link is established by the first RRC procedure for purpose(s),e.g. initial connection establishment/handover. After the first link isestablished successfully, a first cell which the first link is connectedto configures and sends the first RRC message to the UE for further linkestablishment. As a result, based on the first RRC message, the UEperforms the second RRC procedure for establishing at least a linkcorresponding to at least a component carrier. The links established bythe second RRC procedure are used for other purposes, e.g. bandwidthexpansion, RBs establishment, link recovery, etc. The links establishedby the first or second RRC procedure can be configured to connect todifferent cells.

The abovementioned first RRC procedure can be a RRC connectionestablishment procedure, a handover procedure or an inter-RAT procedure.For example, establishment of the first link by the RRC connectionestablishment procedure is initiated by the RRC layer for transmitting aRRC CONNECTION REQUEST message to the first cell. Then, the first cellresponds a RRC CONNECTION SETUP message to the UE to complete the firstlink establishment, and the RRC connection establishment procedure issuccessfully completed. In addition to the RRC connection establishmentprocedure, the first link can be established by an inter-RAT to E-UTRANprocedure when the UE handovers from another RAT, such as a GlobalSystem for Mobile Communications (GSM) system, UTRAN or CDMA2000.

Moreover, the abovementioned second RRC procedure can be a RRCconnection reconfiguration procedure, or a handover procedure, which isinitiated by the first message received from the first cell. If thesecond RRC procedure is the RRC connection reconfiguration procedure,the first message is an RRC CONNECTION RECONFIGURATION message, and anRRC CONNECTION RECONFIGURATION COMPLETE message is sent by the UE tocomplete establishment of the link(s) established by the second RRCprocedure.

Based on the process 30, the UE can firstly establish one linkcorresponding to a component carrier for mobile originating/terminatingcalls or mobile originating signaling. After the first RRC messageindicating further link establishment is received in the first link, theUE establishes at least a link corresponding to at least a componentcarrier for bandwidth extension. Therefore, explicit establishment ofmultiple links with multiple component carriers is provided and therebyefficiency of data transmission can be increased.

Note that, component carriers of the first component carrier and thecomponent carrier (s) established by the second RRC procedure may havethe same component carrier frequency band when corresponding linksconnect to different cells.

Furthermore, the UE can perform a random access procedure for uplinksynchronization and initial cell access. The UE performs at least arandom access procedure for synchronization with the cells associated tothe links established by the second RRC procedure in the followingcases.

In the first case, the UE performs a random access procedure when thelinks established by the second RRC procedure are connected to cell (s)which is different from the first cell. The UE transmits a Random AccessPreamble to each of the cell (s), and each cell responds a Random AccessResponse which includes Timing Alignment information for uplinksynchronization, and a Temporary C-RNTI (Cell Radio Network TemporaryIdentifier) for UE identification.

In addition, the abovementioned Temporary C-RNTI is promoted to C-RNTIwhen the random access procedure is completed. That is, after the UEdetects that the random access procedure is successful, each of thelinks established by the second RRC procedure or by the first RRCprocedure is configured with a C-RNTI for PDCCH (Physical DownlinkControl Channel) receptions, where the C-RNTIs can be the same ordifferent between the links established in the first and second RRCprocedures. Alternatively the C-RNTIs can be configured by the secondRRC procedure for the links established in the second RRC procedure.

In the second case, the UE performs the random access procedure when aRRC message of the second RRC procedure indicating that synchronizationis required is received. That is, the cells associated with the linksestablished by the second RRC procedure decide whether the UE needs therandom access procedure for uplink synchronization, and if the UE needs,transmits the RRC message to indicate the UE to perform the randomaccess procedure.

In the third case, the UE performs the random access procedure when aRRC message of the second RRC procedure excluding uplink timinginformation is received. That is, when the UE has not or cannot derivethe uplink timing information from the RRC message of the second RRCprocedure, the UE performs the random access procedure for uplinksynchronization.

Moreover, the random access procedure can be performed in acontention-based or non-contention-based manner depending on whether aRandom Access Channel (RACH) resource used by the UE is assigned by thecell or randomly selected by the UE itself. For the contention-basedrandom access procedure, the UE performs the random access procedure (asdescribed in the first case) based on a physical random access resourceconfiguration allocated in a specific RRC message of the second RRCprocedure. In addition to the allocation in the RRC message, thephysical random access resource configuration can be allocated in a RRCbroadcast message.

For the non-contention-based random access procedure, the UE performsthe random access procedure for synchronization of the links establishedby the second RRC procedure based on a dedicated random access resourceconfiguration allocated in the first RRC message.

The abovementioned dedicated random access resource configuration caninclude dedicated preamble(s) configured by the cell(s) associated withlink(s) established by the second RRC procedure. According to thededicated preamble(s) assigned by the cells, the UE performs the randomaccess procedure in the non-contention-based manner, which can avoidcontention resolution, and thereby increases the efficiency of therandom access procedure completion.

In addition to the dedicated preamble, the dedicated random accessresource configuration can include a PRACH (Physical Random AccessChannel) Mask Index for indicating subframes which can be transmitted arandom access preamble for synchronization. For example, the PRACH MaskIndex can indicate odd suframes or even subframes for the UE to send therandom access preamble. Therefore, probability of collision with otherrandom access preambles can be decreased, and thereby probability ofsuccess of the random access procedure is increased.

Please refer to FIG. 4, which illustrates a flowchart of a process 40according to a second embodiment of the present invention. The process40 is utilized in the UE for establishing multiple links correspondingto multiple component carriers. The process 40 can be compiled into theprogram code 214 and includes the following steps:

Step 400: Start.

Step 402: Establish a plurality of links corresponding to a plurality ofcomponent carriers by a RRC procedure.

Step 404: End.

According to the process 40, the UE performs a single RRC procedure toestablish a plurality of links corresponding to a plurality of componentcarriers for all of the possible purposes mentioned in the process 30,e.g. for both of initial connection establishment/handover and bandwidthexpansion. Preferably, the RRC procedure is a RRC connectionestablishment procedure, a handover procedure or an inter-RAT to E-UTRANprocedure.

Please note that, some of the plurality of component carriers can havethe same component carrier frequency band when corresponding linksconnect to different cells.

In addition, when establishing the plurality of links corresponding tothe plurality of component carriers, the UE performs a random accessprocedure for synchronization of at least a link. As abovementioned, theUE can perform the random access when a RRC message of the RRC procedureindicating that synchronization is required is received, or when a RRCmessage of the RRC procedure excluding uplink timing information isreceived.

Moreover, the UE performs the random access procedure based on aphysical random access resource configuration, or a dedicated randomaccess resource configuration allocated in a RRC message of the RRCprocedure. The detailed description regarding the random accessprocedure can be referred from the above description. Therefore, therelated detailed description is omitted herein for simplicity.

Furthermore, after the UE detects that the random access procedure isperformed successfully, each of the links established by the RRCprocedure is configured with a C-RNTI (Cell Radio Network TemporaryIdentifier) for PDCCH (Physical Downlink Control Channel) receptions,where the C-RNTIs can be the same or different between the linksestablished in the RRC procedures. Alternatively the C-RNTIs areconfigured by the RRC procedure for the links established in the RRCprocedure.

Based on the process 40, the UE establishes a plurality of linkscorresponding to a plurality of component carriers by a single RRCprocedure for connection establishment, bandwidth extension, etc.

In conclusion, the embodiments of the present invention provideexplicit, appropriate ways for the UE to establish multiple links withmultiple component carriers.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A communication device capable of establishingmultiple links with multiple component carriers in a wirelesscommunication system supporting carrier aggregation, the communicationdevice being configured with a plurality of component carriers of thewireless communication system for realizing carrier aggregation, thecommunication device comprising: a computer readable recording mediumfor storing a program code corresponding to a process; and a processorcoupled to the computer readable recording medium, for processing theprogram code to execute the process; wherein the process comprises:establishing a first link corresponding to a first component carrier ofthe plurality of component carriers, by performing a first radioresource control (RRC) procedure; establishing at least a linkcorresponding to at least a component carrier of the plurality ofcomponent carriers other than the first component carrier, by performinga second RRC procedure which is performed according to a first RRCmessage received in the first link; and performing a random accessprocedure for synchronization of the at least one link established bythe second RRC procedure.
 2. The communication device of claim 1,wherein the first RRC procedure is a RRC connection establishmentprocedure, a handover procedure or an inter-RAT (Radio AccessTechnology) procedure, and the second RRC procedure is a RRC connectionreconfiguration procedure, or a handover procedure.
 3. The communicationdevice of claim 1, wherein performing the random access procedure forsynchronization of the at least one link established by the second RRCprocedure comprises: performing the random access procedure forsynchronization of the at least one link established by the second RRCprocedure when the at least one link established by the second RRCprocedure are connected to at least a cell which is different from afirst cell which the first link is connected to.
 4. The communicationdevice of claim 1, wherein performing the random access procedure forsynchronization of the at least one link established by the second RRCprocedure comprises: performing the random access procedure forsynchronization of the at least one link established by the second RRCprocedure when the first RRC message indicating that synchronization isrequired is received.
 5. The communication device of claim 1, whereinperforming the random access procedure for synchronization of the atleast one link established by the second RRC procedure comprises:performing the random access procedure for synchronization of the atleast one link established by the second RRC procedure when the firstRRC message excluding uplink timing information is received.
 6. Thecommunication device of claim 1, further comprising performing a randomaccess procedure for synchronization of the at least one linkestablished by the second RRC procedure based on a physical randomaccess resource configuration allocated in the first RRC message or in aRRC broadcast message, or based on a dedicated random access resourceconfiguration allocated in the first RRC message.
 7. The communicationdevice of claim 1, wherein the at least one link established by thesecond RRC procedure are configured with the same C-RNTI (Cell RadioNetwork Temporary Identifier) for PDCCH (Physical Downlink ControlChannel) receptions.